1. Field of the Invention
The invention relates to a continuous pusher-type chain for a conveyor having a plurality of rigid pusher elements of novel construction normally extending substantially transversely of the conveying direction and joined together by a series of intervening links. Each series of intervening links includes a pair of strap links rendering the chain capable of double articulation and rendering each pusher element capable of horizontal articulation to a far greater extent than hitherto possible without resort to universal joints or link elements made of flexible material.
2. Description of the Prior Art
The conveyors with which the chain of the present invention is intended to be used have many applications. For purposes of an exemplary showing such conveyors will be described with respect to their use in the mining industry, although their use is not intended to be so limited.
Pusher-type chain conveyors, as used in the mining industry, are found both in the form of separate conveying units and as integral parts of continuous mining machines. A typical continuous mining machine, for example, is self-propelled and is provided at its forward end with cutting means shiftable in such a way that an entry is cut in the material being mined. The entry is so sized as to permit the passage of the mining machine therethrough. Since the cutting operation is a continuous one, means must be provided to move the cut material from in front of the mining machine and to convey it out of the entry. To this end, the mining machine may incorporate several conveyors in its construction, the conveyors acting successively to transport the cut material rearwardly of the machine. Frequently, the mining machine incorporates a "tail conveyor" which is an integral part of the mining machine, located at its rearward end. The purpose of the tail conveyor is to deliver the cut material to other conveying means by which it is removed from the entry. The other conveying means may comprise mine cars, portable belt conveyors, or the like.
The form of tail conveyor most frequently encountered on a continuous mining machine comprises a section of conveyor base means mounted on the mining machine body. One or more additional sections of conveyor base means are connected to and extend beyond the rearward end of the mining machine body. All of the base means sections are characterized by a bottom portion and upstanding side guides or flanges.
In order for the tail conveyor to perform its task properly, the various sections thereof must be capable of both lateral and vertical movement with respect to each other. This enables the cut material to be delivered to a desired point despite changes in orientation of the mining machine as it advances in the entry and changes in level of the entry floor. Similarly, it enables the shifting of the desired delivery point as required.
The tail conveyor incorporates a continuous pushertype conveyor chain which is driven along the length of the conveyor base sections. The chain is normally provided with rigid pusher elements extending transversely of the conveying direction. The pusher elements are located at spaced intervals along the chain, adjacent pusher elements being joined together by a series of link elements. At one end of the tail conveyor, the continuous chain passes over a driven sprocket means, while at the other end it passes over a driven or idler sprocket or roller.
It will be evident from the above description that the conveyor chain must not only be capable of bending in a vertical plane so as to follow the conveyor base sections and to pass over the sprockets, but also it must be capable of bending in a horizontal plane so as to track along the conveyor base sections when they are angularly related, one to another.
Prior art workers have developed numerous types of conveyor chains to meet these requirements. In general, such chains have comprised a plurality of links and interconnecting plates held together by horizontally disposed pintles. The laterally extending pusher elements have been affixed to or formed as a part of selected ones of the chain plates. A number of approaches have been taken to render such chains capable of double articulation. For example, chains have been produced, the parts of which are loosely fitting. Such chains, however, have been characterized by a minimum of horizontal articulation and have generally proven unsatisfactory.
In other embodiments, selected ones of the chain blocks or links have been made in two parts, pivoted to each other by vertical pintles. Thus a sort of universal joint is formed enabling the chain to deflect in the horizontal plane. This construction, however, has proven to have numerous drawbacks including the fact that the necessary abbreviated length and diameter of the vertical pintles has resulted in chain breakage.
In United States Letters Pat. No. 3,155,225 a pusher-type chain is described wherein many of these problems have been overcome. The chain of this patent has special connector links provided at the positions of the pusher elements. These special connectors have, at their adjacent ends, uniquely formed transverse pintle-receiving perforations. The pusher elements each comprise a pair of pushers joined together by a pair of pintles. Each of the pintles joining a pair of pusher elements passes through one of the uniquely formed transverse pintle-receiving perforations of the special connectors. The facing surfaces of the pusher elements of each pair are also specially configured so that the chain is capable of double articulation with a minimum of lost motion, a minimum of wear and without loss of strength.
The chains taught in the above mentioned United States Letters Patent have been characterized by superior performance in the field. While ample to enable such chains to track in the conveyor base sections, the amount of horizontal articulation of which the pusher elements are capable is nonetheless limited. It is not unusual during the conveying operation for an obstruction to become lodged or to accumulate at one edge or the other of a conveyor base section. Unless each of the pusher elements can override or dodge around such an obstruction, the obstruction can result in breakage of one or more pusher elements or the chain itself. Furthermore, during the attempt by a pusher element to twist horizontally to pass about such an obstruction, the chain is shortened, causing considerable stress on the chain.
The present invention is directed to a pusher chain which has all the advantages of double articulation without the use of loose chain parts, universal joints or link elements made of flexible material. Furthermore, the pusher elements of the chain of the present invention are capable of far greater horizontal articulation than those of U.S. Pat. No. 3,155,225 thereby enabling them to dodge obstructions at one edge or the other of a conveyor base section with a minimum shortening of the chain and a minimum stress upon the chain. The chain construction is such that the pusher elements tend to be self-righting, i.e., to return to their normal positions transverse the conveying direction. Furthermore, as will be shown hereinafter, the teachings of the present invention are applicable to chains of the type taught in the above mentioned United States Letters Patent.
The chain of the present invention is simple in construction, easy and inexpensive to manufacture and characterized by superior strength. The chain can be designed to have any desired pitch and the degree of horizontal articulation can also be controlled by design, depending upon the use for which the chain is intended. When required, the pusher elements or the various link elements of the chain may be more quickly and easily replaced. Furthermore, the invention contemplates the provision of novel pusher elements which may be more easily and inexpensively manufactured and which lend versatility to the chain design, as will be described hereinafter.